As typical heavy machinery widely used at construction sites, an excavator is capable of conducting various works using a variety of attachments such as a bucket, a crusher, a breaker, and grab, which can be attached or detached according to the purpose of work. Such an attachment is detachably coupled to an arm of the excavator using a coupler, and thus can be replaced with another type of attachment according to the purpose of work of the excavator.
FIG. 1 is a diagram illustrating an example of a conventional attachment coupler for heavy machinery. Referring to FIG. 1, coupler 10 includes a coupler body 11, a fixed hook 12 installed under the coupler body 11, a movable hook 13 rotatably installed under the coupler body 11, and a hydraulic cylinder 14 for rotating the movable hook 13.
When a cylinder rod 14a of the hydraulic cylinder 14 is extended such that a second coupling pin 22 is locked into a coupling groove of the movable hook 13 while a first coupling pin 21 of the attachment 20 is being locked into a coupling groove of the fixed hook 12, the attachment 20 is coupled to an arm 1 of an excavator. When the cylinder rod 14a of the hydraulic cylinder 14 is contracted such that the second coupling pin 22 of the attachment is unlocked from the coupling groove of the movable hook 13, the attachment 20 is detached from the arm 1 of the excavator. Accordingly, the attachment 20 can be attached or detached using the coupler 10 installed on the arm 1 of the excavator.
However, in the above conventional coupler 10, if the pressurized oil supplied to the hydraulic cylinder 14 leaks, the cylinder rod 14a is broken or the movable hook 13 is damaged, the attachment 20 can be accidently separated from the coupler 10.
In other words, if the pressurized oil supplied to the hydraulic cylinder 14 leaks while the first and second coupling pins 21 and 22 are locked respectively into the fixed hook 12 and the movable hook 13, the cylinder rod 14a contracts at a speed corresponding to the amount of leaking oil. Accordingly, as the movable hook 13 of the coupler 10 removes a force restricting the second coupling pin 22 of the attachment 20, the first and the second coupling pins 21 and 22 are respectively unlocked from the fixed hook 12 and the movable hook 13. Hence, the attachment 20 can be separated from the coupler 10.
In the same manner, when the cylinder rod 14a breaks, a force restricting the second coupling pin 22 is removed from the movable hook 13 and thus the attachment 20 can be is separated from the coupler 10.
In addition, in the prior art, there is no way of confirming whether the attachment 20 has been completely coupled to the coupler 10. Thus, the attachment 20 may be incompletely coupled to the coupler 10, thereby sometimes being accidently separated from the coupler 10. Moreover, to confirm whether the attachment 20 has been completely coupled to the coupler 10, an operator needs to leave the operating seat and manually check or to ask another operator for help to check.